What caused the sudden spike in latency for Datadog's APM service in the US West region yesterday afternoon?

Introduction

The sudden spike in latency for Datadog's APM service in the US West region yesterday afternoon is a critical issue that demands immediate attention and thorough analysis. As we dive into this product root cause analysis, we'll systematically investigate potential factors contributing to this performance degradation, aiming to identify the underlying cause and develop both short-term fixes and long-term preventive measures.

Step 1

Clarifying Questions (3 minutes)

• Looking at the regional nature of the issue, I'm wondering about potential infrastructure problems. Has there been any recent changes or maintenance in our US West data centers?

Why it matters: Infrastructure changes often correlate with performance issues. Expected answer: Recent server upgrades or network reconfigurations. Impact on approach: If confirmed, we'd focus on infrastructure-related hypotheses.

• Considering the timing, I'm curious about any recent code deployments. Were there any updates pushed to the APM service in the last 24-48 hours?

Why it matters: New code can introduce unexpected latency. Expected answer: Details of recent deployments, if any. Impact on approach: If there were deployments, we'd prioritize code-related hypotheses.

• Thinking about user behavior, I'm interested in usage patterns. Have we seen any unusual spikes in traffic or changes in user activity in the US West region?

Why it matters: Unexpected load can strain systems and cause latency. Expected answer: Traffic patterns and any anomalies. Impact on approach: Abnormal traffic would lead us to investigate capacity and scaling issues.

• Considering the broader ecosystem, I'm wondering about dependencies. Have any of our third-party services or APIs reported issues during this timeframe?

Why it matters: External dependencies can significantly impact our service performance. Expected answer: Status of integrated services and APIs. Impact on approach: Issues with dependencies would shift our focus to integration points and fallback mechanisms.